The Trane SEN1519 3-Speed Fan Sensor is a control device that monitors and regulates fan motor speed in HVAC systems. It works by detecting the fan’s rotational performance and communicating with the control board to adjust speeds for optimal airflow. Used in air handlers, rooftop units, and packaged systems, it enhances system efficiency, balances airflow, reduces energy consumption,... https://www.partshnc.com/3speed-fan-sensor-5